Free-Surface Flow Simulations with Smoothed Particle Hydrodynamics Method using High-Performance Computing

Today, the use of modern high-performance computing (HPC) systems, such as clusters equipped with graphics processing units (GPUs), allows solving problems with resolutions unthinkable only a decade ago. The demand for high computational power is certainly an issue when simulating free-surface flows. However, taking the advantage of GPU’s parallel computing techniques, simulations involving up to 109 particles can be achieved. In this framework, this chapter shows some numerical results of typical coastal engineering problems obtained by means of the GPU-based computing servers maintained at the Environmental Physics Laboratory (EPhysLab) from Vigo University in Ourense (Spain) and the Tier-1 Galileo cluster of the Italian computing centre CINECA. The DualSPHysics free package based on smoothed particle hydrodynamics (SPH) technique was used for the purpose. SPH is a meshless particle method based on Lagrangian formulation by which the fluid domain is discretized as a collection of computing fluid particles. Speedup and efficiency of calculations are studied in terms of the initial interparticle distance and by coupling DualSPHysics with a NLSW wave propagation model. Water free-surface elevation, orbital velocities and wave forces are compared with results from experimental campaigns and theoretical solutions

A DEM approach for simulating flexible beam elements with the Project Chrono core module in DualSPHysics

This work presents a novel approach for simulating elastic beam elements in DualSPHysics leveraging functions made available by the coupling with the Project Chrono library. Such numerical frameworks, belonging to the Meshfree Particle Methods family, stand out for several features, like complex multiphase phenomena, moving boundaries, and high deformations which are handled with relative ease and reasonable numerical stability and reliability. Based on a co-rotating rigid element structure and lumped elasticity, a cogent mathematical formulation, relying on the Euler–Bernoulli beam theory for the structural discretization, is presented and applied to simulating two-dimensional flexible beams with the discrete elements method (DEM) formulation. Three test cases are presented to validate the smoothed particle hydrodynamics-based (SPH) structure model in both accuracy and stability, starting from an equilibrium test, to the dynamic response, and closing with a fluid–structure interaction simulation. This work proves that the developed theory can be used within a Lagrangian framework, using the features provided by a DEM solver, overtaking the initial limitations, and hence applying the results of static theories to complex dynamic problems.Xunta de Galicia | Ref. ED431C 2021/44Xunta de Galicia | Ref. ED481A-2021/337Ministerio de Ciencia, Innovación y Universidades | Ref. IJCI-2017-32592Agencia Estatal de Investigación | Ref. PID2020-113245RB-I0

Regular wave seakeeping analysis of a planing hull by smoothed particle hydrodynamics: a comprehensive validation

In this work, the dynamics of a planing hull in regular head waves was investigated using the Smoothed Particle Hydrodynamics (SPH) meshfree method. The simulation of the interaction of such vessels with wave trains features several challenging characteristics, from the complex physical interaction, due to large dynamic responses, to the likewise heavy numerical workload. A novel numerical wave flume implemented within the SPH-based code DualSPHysics fulfills both demands, guaranteeing comparable accuracy with an established proprietary Computational Fluid Dynamics (CFD) solver without sharpening the computational load. The numerical wave flume uses ad hoc open-boundary conditions to reproduce the flow characteristics encountered by the hull during its motion, combining the current and waves while adjusting their properties with respect to the vessel’s experimental towing speed. It follows a relatively small three-dimensional domain, where the potentiality of the SPH method in modeling free-surface flows interacting with moving structures is unleashed. The results in different wave conditions show the feasibility of this novel approach, considering the overall good agreement with the experiments; hence, an interesting alternative procedure to simulate the seakeeping test in several marine conditions with bearable effort and satisfying accuracy is established.Ministerio de Ciencia e Innovación | Ref. PID2020-113245RBI00Xunta de Galicia | Ref. ED431C 2021/44Ministerio de Ciencia e Innovación | Ref. TED2021-129479AI00Xunta de Galicia | Ref. ED481A-2021/337Ministerio de Ciencia e Innovación | Ref. RYC2020-030197-

Efficiency and survivability analysis of a point-absorber wave energy converter using DualSPHysics

Smoothed Particle Hydrodynamics (SPH) method is used here to simulate a heaving point-absorber with a Power Take-Off system (PTO). The SPH-based code DualSPHysics is first validated with experimental data of regular waves interacting with the point-absorber. Comparison between the numerical and experimental heave displacement and velocity of the device show a good agreement for a given regular wave condition and different configurations of the PTO system. The validated numerical tool is then employed to investigate the efficiency of the proposed system. The efficiency, which is defined here as the ratio between the power absorbed by the point-absorber and its theoretical maximum, is obtained for different wave conditions and several arrangements of the PTO. Finally, the effects of highly energetic sea states on the buoy are examined through alternative configurations of the initial system. A survivability study is performed by computing the horizontal and vertical forces exerted by focused waves on the wave energy converter (WEC). The yield criterion is used to determine that submerging the heaving buoy at a certain depth is the most effective strategy to reduce the loads acting on the WEC and its structure, while keeping the WEC floating at still water level is the worst-case scenario.Agencia Estatal de Investigación | Ref. ENE2016-75074-C2-1-RAgencia Estatal de Investigación | Ref. IJCI-2017-32592Xunta de Galicia | Ref. ED431C 2017/6

Recent development on the seismic devices for steel storage structures

Goods and products are stored in framed systems, such as pallet racks, used for industrial and commercial ac-tivities. In the last years, pallet rack code provisions for seismic loads have been significantly improved, but there are still relevant aspects that need attention for guaranteeing a safer structural design. For example, in the current European and American standards, no indications are given about the seismic isolation systems applied to these structures. Only two ways to enhance the performance of racks in seismic zones are reported: rack netting and structural strengthening. Both methodologies present logistic and technical problems. For this reason, researchers are investigating more efficient solutions, like the base isolation systems. An accurate isolation system can bring benefits in terms of reduction of the structural damage and improving the safety of the stored items. Since the cost of the structural frame is often negligible, with respect to the cost of the stored products, avoiding the overturning of merchandise is an important challenge. Moreover, falling pallets can bring to the overall global collapse due to an impact given on beams or columns. In the paper, a critical overview of base isolation systems developed for different steel storage rack typologies is presented and discussed, high-lighting the main characteristics and the advantages associated with their use in practical cases. Furthermore, four different applications of energy dissipation devices are briefly discussed, comparing these systems with the previously introduced device

An Optimal Seismic Force Pattern for Uniform Drift Distribution

The force distribution proposed by codes, which in many cases is framed in the equivalent static force procedure, likely leads to design structures with non-uniform drift distribution in terms of inter-storey drift and ductility demands. This can lead to an unbalanced drift demand at certain storeys. This phenomenon may also amass cyclic damage to the dissipative elements at this very storey, therefore increasing the probability of premature failure for low-cycle fatigue. This work proposes a new force design distribution that accounts for higher mode effects and limits the displacement concentration at any storey thus improving the dissipative capacity of the whole structures. The main advantage of the proposed method stands in its formulation, which allows to spare any previous set up with structural analyses. The proposed force distribution has been applied to multi-degree-of-freedom systems to check its effectiveness, and the results have been compared with other proposals. In addition, in order to obtain a further validation of the proposed force distribution, the results obtained by using a genetic algorithm have been evaluated and compared. Additionally, the results provided in this work validate the proposed procedure to develop a more efficient lateral load pattern

Application of an SPH-DEM Coupled Model for Elastic Fluid–Structure Interaction

In this work, we present the application of an alternative numerical model for fluid dynamic analyses of structural systems within the Smoothed Particle Hydrodynamics (SPH) framework of DualSPHysics coupled to the Project Chrono library. The Discrete Elements Method-based (DEM) structure model relies on the Euler–Bernoulli theory and utilizes lumped elasticity and rigid body dynamics to reproduce the flexural behavior of two-dimensional beams. The structure and fluid domain are both discretized with SPH particles: the fluid dynamics obey a Weakly Compressible SPH (WCSPH) formulation, whereas the structure particles are assembled into DEM rigid elements, moving according to physically-based, properly developed rotational dynamics. The presented model is of interest for studying complex soil–, solid–, fluid–structure interactions, involving a system that includes all the aforementioned phases in a unitary context—very useful for studying engineered structures under the threat of hazardous natural events. Test cases are presented to validate the SPH-DEM coupled model in both accuracy and stability, starting from an equilibrium test, to the dynamic response, and ending with fluid–structure interaction simulations. This work proves that the developed theory can be used within a Lagrangian framework, using the features provided by a DEM solver, overtaking the intrinsic limitations, and hence applying the results of static theory to complex dynamic problem